Carburetor for internal combustion engines



July 31, 1962 P. LANDRUM CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed Aug. 3, 1959 2 Sheets-Sheet l INVENTOR. Porter Landmm Rttorneys July 31, 1962 t e e h 4 S t 6 sm s m2 G TIE INVENTOR. Porter La ndrum :Spe eJ MP H.

United states 3,047,277 Patented July 31, 1962' line My invention relates to carburetors for internal combustion engines.

In the carburetionof liquid fuel such as gasoline for internal combustion engines, it is known that the burning efficiency under pressure is directly affected by the fineness of atomization of the gasoline by the carburetor. That is, gasoline not finely atomized will not fully vaporize and hence any unvaporized fuel drawn into a cylinder and compressed will not burn with any appreciable degree of thermal efiiciency.

In carburetors as currently produced atomization of the fuel is produced by inspirating a small stream of gasoline into the main air passage by reducing the pressure in the air passage at the point of discharge of the fuel stream into the main air stream. This is accomplished by providing a venturi to increase the velocity of the main air stream, thus to reduce its pressure, thereby to draw the liquid gasoline through a small opening located in the area of reduced pressure, highvelocity air flow.

Present day automotive and truck engines using gasoline have become so large that the carburetors therefor in turn must have very large air passages in order to supply the quantity of air-fuel necessary to meet the engine demand at full throttle. Since these engines are extremely powerful at full throttle it is only necessary for the throttle valve to be partially open during most of the time of the operation, for instance at cruising.

speed of the vehicle. A=t cruising speed the velocity of air in such carburetors is so low that in the fuel supply areas proper atomization of the fuel is not obtained. Hence, improper air-fuel mixture prevails during the major time of operation of such engines, resulting in high fuel consumption, a large part of which fuel is wasted by simply going out of the engine exhaust in an incompletely burned state.

Still further, in present carburetors and when cruising, the main fuel system supplies the majority of the air-fuel mixture and the rest is supplied from the idling fuel system. As now constructed the throttle valve is positioned in the air passage so that a part of the air-fuel mixture from the main jets passes through the main air passage on the side of the passage opposite the entrance thereinto of the idling jets. Therefore, at cruising, as now constructed, complete admixing and complete vaporization of both the main air fuel stream and the idling jet fuel air streams is impossible, resulting in an output stream of air-fuel from the carburetor which is not properly conditioned for combustion. In the average 1959 American made automobile this condition exists throughout the full cruising range to about 70 miles per hour.

In view of the foregoing, the prime object of my invention is to provide a carburetor in which, in all ranges of throttle valve opening, the fuel is placed in the mainair stream at the point or points of highest velocity of the air stream, assuring improved atomization, aflfording opportunity for more complete vaporization, and increasing fuel economy.

A more specific object is to provide a carburetor in which the main air fuel stream is combined with and intimately mixed with the air-fuel stream of the idling system, this preferably being accomplished by restricting or baffling the air passage downstream of the throttle valve in such manner that in the cruising range substantially all of the intake passes by the throttle valve on discharge.

the side of the main air passage at which the idling jets A further object is to provide a carburetor in which, in practical operational effect, the throttle valve forms a variable venturi, which increases or decreases in area according to power demandyof the engine up to about 30% of full power.

A carburetor illustrating features of my invention is shown in the accompanying drawings which:

FIG. 1 is a vertical cross sectional View of a somewhat standard downdraft carburetor having my invention applied thereto;

FIG. 2 is a cross sectional view of the throttle valve control section of the carburetor at part throttle;

FIG. 3 is a view similar to FIG. 2 showing the throttle valve more fully opened;

FIG. 4 is a detail sectional view taken along line 4,4 of FIG. 1 with certain of the parts broken away for the sake of clarity;

FIG. 5 is a view corresponding generally to FIG. 2 and somewhat enlarged, and illustrating a modified form of my invention with the throttle valve fully closed;

FIG. 6 is a view corresponding to FIG. 5 with the throttle valve in full opened position;

FIG. 7 is a detail sectional view taken along line 77 of FIG. 5 with the throttle valve partly broken away; and,

HG. 8 is a graph illustrating the improvement in fuel economy obtained by my invention.

Referring to FIG. 1 of the drawings I show my inven tion in association with a carburetor having a fuel supply chamber Ill controlled by the usual float 11 and float valve 12. Gasoline in liquid form is maintained in the well 13 up to the level indicated. The main jets 14 are located in the middle of the main passage 16 down which air flows in the manner illustrated by the arrows.

The lower section of the carburetor embodies the usual butterfly throttle valve 17 mounted on an operating shaft 18. An idling jet 21 is located on .a side of the lower part '16 of the main air passage, generally in the position quite customary for prior carburetors. An idling adjustment screw 22 is provided.

My invention comprises meansdownstream of the valve 17 fior restricting the main air passage 16*. To this end I provide a crescent-shaped restriction 23 which is located on the side wall of the 'air passage 16* opposite the idling jet 21. In addition, there may be additional fuel openings which are located just above the idling jet 21 and which are designated by the numerals 24 and 26.

Referring particularly to FIG. 2 it will be seen that the restriction 23 is struck on the turning radius of the butterfly valve, that is, from the center of the valve shaft 18. In way the flow of air around the butterfly valve is restricted to that portion of the passage which is adjacent the openings 21, 24 and 26 because the edge of the valve coacting with the curved surface substantially seals that side of the opening.

In the position shown in FIG. 1 the throttle valve is in idling position. Under these conditions it will be seen that some of the being drawn past the periphery of the butterfly valve will inspirate from the jet openings suflicient fuel to keep the engine idling. As soon as the throttle valve opens away from the idling position, and within the range of opening illustrated in FIG. 2., the righthandmost side of the butterfly valve as illustrated in FIG. 2 still is in substantially air sealing contact with the bafiie 23. Under these conditions substantially all of the air flowing down the passage "16 must pass by the exits of the several idling jet openings. It thus be seen that such amount of fuel as already is in the air entering the passage 16 and which has been inspirated thereinto from the main jet 14, is again subjected to the high velocity, low pressure action adjacent the exits of the idling jet openings. Therefore, I obtain intimate admixing and further atomization of the main jet fuel and mixing therewith of that amount of fuel inspirated from the idling jet openings.

The condition just described obtains in part when the throttle valve is in the position shown in FIG. 3. That is, since the restriction 23 is crescent shaped, it will be apparent that the larger volume of the total air flows past the mouths of the idling jet openings, and only a minor part passes through the space defined between the lower part of the butterfly valve and the crescent shape of the restriction 23. At full throttle opening it will be apparent that the effect of the restriction 23 is substantially eliminated whereby very little fuel is drawn through the idling jet system and practically all of it is supplied through the main jet system.

In FIGS. 5, 6 and 7 I show a modified form of the invention in which the restriction 23 takes the shape of a diametrically extending wall and in which there is a curved surface 27 which cooperates with the lowermost side of the valve 17 in all positions therof. Under these conditions it will be seen that the butterfly valve only permits air to flow from the carburetor lower section along the lefthandmost wall thereof as viewed in FIGS. and 6, that is, along the wall through which exit the openings of the idling jet system. This modification of my invention affords even more marked admixing and finer atomization of the fuel in the cruising range, which is up to approximately the valve opening position indicated in dotted lines in FIG. 6. In practice I have found that the eflective areas of the exit opening 28 should be about 1.2 times the minimum area at the throat 29 of the venturi of the carburetor. This maintains the very much standard ratio so that at full throttle the eflfect of the restriction 23 as such is not effective. With either modification the throttle valve is substantially balanced while coacting with the baflle.

From the foregoing it will be apparent that I have devised an improved carburetor. In actual tests with a 1956 eight-cylinder Chevrolet automobile, equipped with the standard automatic transmission and double barrel carburetor, made by the Rochester Products Company, Rochester, New York, I note the improvement in fuel economy shown in the graph of FIG. 8. These tests were made by using the same carburetor in both instances,

4 and modifying it by providing the bafile of the kind illustrated at 23 in FIGS. 1 to 4, inclusive. Curve 31 will be seen to indicate generally about 12% increase in fuel economy over the standard carburetor indicated by the curve 32. No decrease in performance was noted.

While I have shown my invention in but two forms, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications Without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

l. The combination with a carburetor having a main air inlet passage and a butterfly valve therein together with fuel discharge passages opening into the main air passage adjacent the butterfly valve, of a baffle immediately downstream from the butterfly valve having its upper surface struck substantially on the turning radius of the butterfly valve and cooperable therewith as the butterfly valve opens to restrict said main air passage, said baflie being effective to restrict that side of the main air passage opposite the entrance of the fuel discharge passages, whereby as the butterfly valve opens a stream of high velocity air passes by the discharge ends of the fuel discharge passages.

2. The combination with a carburetor having a main air inlet passage and a butterfly valve therein together with fuel discharge passages opening into the main air passage adjacent the butterfly valve, of means to restrict the main air passage comprising a baflle located immediately downstream from the butterfly valve and which extends substantially one-half way across the main air passage and has a curved upper surface struck substantially on the turning radius of the butterfly valve, thereby substantially to seal the side of the main air pasasge opposite the fuel discharge passages, whereby as the butterfly valve opens a stream of high velocity air passes by the discharge ends of the fuel discharge passages.

References Cited in the file of this patent UNITED STATES PATENTS 2,752,131 Gretz June 26, 1956 2,798,705 Lawrence July 9, 1957 2,877,003 Goodridge et al Mar. 10, 1959 

